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Description/Abstract

Eysenbach's (2006) study in PloS Biology on 1492 articles published during one 6-month period in one journal (PNAS) found that the Open Access (OA) articles were more cited than the non-OA ones. The online bibliography on the OA citation advantage http://opcit.eprints.org/oacitation-biblio.html records a number of prior within-journal comparisons that found exactly the same effect: freely available articles are read and cited more. Eysenbach’s further finding that the OA advantage (in this particular 6-month, 3-option, 1-journal PloS/PNAS study) is greater for articles that have paid for OA publication than for those that have merely been self-archived will require replication on much larger samples as most of the prior evidence for the OA advantage comes from self-archived articles and is based on sample sizes four orders of magnitude larger for both the number of articles and the number of journals tested.